1. Field of the Invention
This invention relates generally to an all-optical Code Division Multiple Access (CDMA) system and, more particularly, to a methodology and a concomitant system for a holographic CDMA switch.
2. Description of the Background Art
The ever-increasing demand for very high rate services is driving the evolution of future telecommunication infrastructure towards an all-optical network. In effect, an all-optical network is a network in which there is no conversion of optical signals to electrical signals for establishing key network functions. Among many network functions in an all-optical network that need to be implemented in the optical domain is the interconnection/switching system.
Globally, optical interconnections may be categorized as either material-guided light switches or free-space optical switches, with the latter being more powerful because of their high-density connectivity arising from spatial parallelism and three-dimensional structure. Among various types of free-space photonic switches, optical switches based on holographic techniques have been recently introduced. For example, the article entitled “Holographic Optical Switch: The Roses Demonstrator” by W. A. Grossland et. al., IEEE Journal of Lightwave Technology, Vol. 18, No. 12, December 2000, reports the results of a demonstration of a prototype 1×8 free-space switch using re-configurable holograms. The space-variant optical interconnection system based on spatial-phase CDMA technique with multiplexed Fourier holography has been described in the article entitled “Spatial-phase code-division multiple-access system with multiplexed Fourier holography switching for reconfigurable optical interconnection”, by Takasago et al., Applied Optics, Vol. 39, No. 14, May 2000, where a one-dimensional phase code has been used and a routing pattern has been recorded in a Fourier hologram in order to decode and route simultaneously the signals into the specific addresses. The performance of this switch measured by the signal-to-noise ratio is about 5 for managing more than 250 routing patterns.
However, the art is devoid of a simple free-space switch with: (1) better performance and less loss than known optical switches; (2) a high processing gain; and (3) simplicity of two-dimensional signature code generation.